Rapid urbanization means that a huge number of people now
inhabit small areas. If ten million people live in a city and they all
operate their own automobiles, the streets would become just one gigantic
parking lot with no one going anywhere. Therefore, good urban planning should
encourage the use of public transportation as much as possible. Of course,
public transportation has to be made appealing for the general public, of which
the aspects of cost, convenience, comfort and safety are the most
important.

To make public transportation convenient, comfortable and safe
means the investment of money. If these investments were expected to be
totally recouped by passenger fares, these systems may be cost-prohibitive to
consumers. Therefore, very often, such systems are subsidized by the government in the form of direct aid or tax
relief. Another way of
subsidizing public transportation is to sell advertising space on
bus/train/trolley exteriors and interiors, stops, stations and terminals.
In this note, we will concentrate on bus-exterior advertising.

For advertisers, there are many advantages for bus-exterior
advertising, including the fact that target group can be geographically based
as determined by certain bus routes. For a local advertiser, this avoids
the huge wastage involved in broadcast media. The ad exposure may also
trigger an immediate sale (e.g. to stop to get gasoline refill or refreshments) at a moment when
no other media are present.

We will now cite some survey data from the TGI Brasil
study. This is a survey of 10,624 persons between the ages of 12 to 64
years old who were interviewed during 2001 in Brazil. According to this
survey, 33.8% of the survey respondents recalled that they have seen a painted
bus exterior ad during the past 7 days.

One of the drawbacks of transportation-based advertising is
that it is impossible to target a specific group. As a result, the ads may
end up reaching a large number of people who are not prospects for the
advertised product or service. For example, if the advertisement is for a
gasoline brand, it may have an impact on drivers who see that ad, but it will
have no value for all the pedestrians or public transport commuters who do not
use automobiles. Now the same can be said of telenovelas as advertising
vehicles for laundry detergents, as there are presumably telenovela audience
members who are not responsible for laundry duties; still, it is possible to
document the size and composition of the telenovela audience to indicate that it
is relatively efficient (see Telenovelas and Soap in Latin
America). We would like to do the same for bus-exterior advertising
here.

For the present case, we present first the ad exposure rate by
age/sex groups in the next chart. The rate is certainly not constant
across these groups, as young females and young/middle-aged males are more
likely to come across them. At the very least, we can say that laundry
detergent, which is traditionally targeted towards middle-aged women, is
probably not a good bet for bus-exterior advertising.

In the next chart, we show the exposure rates by the
educational level and the socio-economic status of the survey respondents.
Clearly, the audience for bus-exterior ads is skewed towards the affluent and
better educated. There may be many reasons for this. One possible
reason is that automobile drivers who are stuck in traffic have nothing to do
but look around, whereas pedestrians in crowded streets probably do not quite
pay similar attention to the car traffic.

Our final consideration is an obvious one --- the exposure
rates by the average total distance of weekly commutation. According to the next
chart, those who have to travel long distances are much
more likely to remember seeing bus-exterior advertisements. In fact, we
are surprised that anyone who travels more than 400km per week could possibly
avoid being exposed to bus-exterior ads.